From: Christoph Hellwig <hch@infradead.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: npiggin@suse.de, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [patch 12/14] fs: dcache per-bucket dcache hash locking
Date: Mon, 30 Mar 2009 14:00:31 -0400 [thread overview]
Message-ID: <20090330180031.GB1041@infradead.org> (raw)
In-Reply-To: <878wmnnr73.fsf@basil.nowhere.org>
On Mon, Mar 30, 2009 at 02:14:08PM +0200, Andi Kleen wrote:
> npiggin@suse.de writes:
>
> > We can turn the dcache hash locking from a global dcache_hash_lock into
> > per-bucket locking.
>
> Per bucket locking is typically a bad idea because you get far too
> many locks and you increase cache footprint with all of them. It's
> typically better to use a second much smaller hash table that only has
> locks (by just shifting the hash value down some more)
> Just need to be careful to avoid too much false sharing.
Yeah, I'm also not too happy about it. I think we're better off
replacing the global hash with more fine-grained structures. That might
even some sort of simplistic tree hanging of directory dentries.
The hard part in getting anything like this done was always the amount
of different things dcache_lock protects besiseds the hash, but Nick's
earlier patches when actually fully implemented should sort that out.
next prev parent reply other threads:[~2009-03-30 18:00 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-29 15:55 [rfc] scale dcache locking npiggin
2009-03-29 15:55 ` [patch 01/14] fs: dcache fix LRU ordering npiggin
2009-03-29 15:55 ` [patch 02/14] fs: dcache scale hash npiggin
2009-03-29 15:55 ` [patch 03/14] fs: dcache scale lru npiggin
2009-03-29 15:55 ` [patch 04/14] fs: dcache scale nr_dentry npiggin
2009-03-29 15:55 ` [patch 05/14] fs: dcache scale dentry refcount npiggin
2009-03-29 15:55 ` [patch 06/14] fs: dcache scale d_unhashed npiggin
2009-03-29 15:55 ` [patch 07/14] fs: dcache scale subdirs npiggin
2009-03-29 15:55 ` [patch 08/14] fs: scale inode alias list npiggin
2009-03-30 12:18 ` Andi Kleen
2009-03-30 12:31 ` Nick Piggin
2009-03-29 15:55 ` [patch 09/14] fs: use RCU / seqlock logic for reverse and multi-step operaitons npiggin
2009-03-30 12:16 ` Andi Kleen
2009-03-30 12:29 ` Nick Piggin
2009-03-30 12:43 ` Andi Kleen
2009-03-29 15:55 ` [patch 10/14] fs: dcache remove dcache_lock npiggin
2009-03-29 15:55 ` [patch 11/14] fs: dcache reduce dput locking npiggin
2009-03-29 15:55 ` [patch 12/14] fs: dcache per-bucket dcache hash locking npiggin
2009-03-30 12:14 ` Andi Kleen
2009-03-30 12:27 ` Nick Piggin
2009-03-30 12:47 ` Andi Kleen
2009-03-30 12:59 ` Nick Piggin
2009-03-30 18:00 ` Christoph Hellwig [this message]
2009-03-31 1:57 ` Nick Piggin
2009-03-29 15:55 ` [patch 13/14] fs: dcache reduce dcache_inode_lock npiggin
2009-03-29 15:55 ` [patch 14/14] fs: dcache per-inode inode alias locking npiggin
2009-04-01 14:23 ` [rfc] scale dcache locking Al Viro
2009-04-02 9:43 ` Nick Piggin
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